Polyamide-imide-based film, process for preparing the same, and cover window and display device comprising the same

Abstract

The embodiments aim to provide a polyamide-imide-based film that has a TGA weight loss area value (TDA) of 0.01%·min/° C. or less and is excellent in mechanical properties, optical properties, and the suitability for post-processing, a process for preparing the same, and a cover window and a display device comprising the same.

1 . A polyamide-imide-based film, which has a TGA weight loss area value (TDA) of 0.01%·min/° C. or less. 
     
     
         2 . The polyamide-imide-based film of  claim 1 , wherein the first weight loss temperature (Tw) of the film in a TGA analysis is 290° C. or higher. 
     
     
         3 . The polyamide-imide-based film of  claim 1 , wherein the 1% weight loss temperature (Td1) of the film in a TGA analysis is 300° C. or higher. 
     
     
         4 . The polyamide-imide-based film of  claim 1 , wherein the 5% weight loss temperature (Td5) of the film in a TGA analysis is 420° C. or higher. 
     
     
         5 . The polyamide-imide-based film of  claim 1 , wherein the film has an adhesion to a hard coating layer of 5B. 
     
     
         6 . The polyamide-imide-based film of  claim 1 , wherein when the film is immersed in an MIBK solvent for 5 seconds, dried at 80° C. for 3 minutes, and then measured for haze, the change in haze (ΔHz M ) is 0.2% or less. 
     
     
         7 . The polyamide-imide-based film of  claim 1 , wherein when the film is immersed in an IPA solvent for 5 seconds, dried at 80° C. for 3 minutes, and then measured for haze, the change in haze (ΔHz I ) is 0.1% or less. 
     
     
         8 . The polyamide-imide-based film of  claim 1 , wherein the film comprises a polyamide-imide-based polymer, and the polyamide-imide-based polymer comprises an imide-based repeat unit and an amide-based repeat unit at a molar ratio of 2:98 to 70:30. 
     
     
         9 . The polyamide-imide-based film of  claim 1 , wherein the film has a surface tension of a first side of 40 dyn/cm or more. 
     
     
         10 . The polyamide-imide-based film of  claim 1 , which, based on a thickness of the film of 50 μm, has a modulus of 5 GPa or more, a transmittance of 80% or more, a haze of 1% or less, and a yellow index of 5 or less. 
     
     
         11 . A cover window for a display device, which comprises a polyamide-imide-based film and a functional layer, wherein the polyamide-imide-based film has a TGA weight loss area value of 0.01%·min/° C. or less. 
     
     
         12 . A display device, which comprises a display unit; and a cover window disposed on the display unit, wherein the cover window comprises a polyamide-imide-based film and a functional layer, and the polyamide-imide-based film has a TGA weight loss area value of 0.01%·min/° C. or less. 
     
     
         13 . A process for preparing the polyamide-imide-based film of  claim 1 , which comprises:
 polymerizing a diamine compound, a dianhydride compound, and a dicarbonyl compound in an organic solvent to prepare a polyamide-imide-based polymer solution;   casting the solution to prepare a gel sheet; and   thermally treating the gel sheet.   
     
     
         14 . The process for preparing the polyamide-based film according to  claim 13 , wherein the step of thermally treating the gel sheet comprises a first thermal treatment step, a first cooling step, a second thermal treatment step, a third thermal treatment step, a second cooling step, and a third cooling step, which are sequentially carried out.